This invention relates to a cylinder head for an internal combustion engine and more particularly to an improved cylinder head for a multi valve internal combustion engine.
The trend in modern engines and particularly high performance automotive engines is toward multiple valves that are operated by overhead mounted camshafts. Although four valve twin overhead camshaft engines are quite common, there is a desire for further increase of performance and efficiency through the use of a greater number of valves. Although five valve engines have been proposed, the addition of a third intake valve, as is typical with five valve practice, presents a number of problems.
One of the problems in conjunction with the provision of five intake valves for a single cylinder of an internal combustion engine is that if the valves are directly actuated through thimble tappets, then the cylinder head fasteners tend to interfere with the tappet guides, particularly on the intake side of the engine. To overcome these difficulties and to facilitate cylinder head attachment to the cylinder block, it has been the practice to employ a multi part cylinder head assembly, including a main cylinder head and a cam carrier that is affixed to the cylinder head and which forms the tappet guides. Although this type of arrangement is highly satisfactory, it has been the practice to mount the cylinder head attachment bolts under the cam carrier and hence the cam carrier must be removed in order to service the cylinder head bolt. In addition, the use of two separate castings gives rise to certain other problems which should be self evident.
It is, therefore, a principal object of this invention to provide an improved cylinder head assembly for an internal combustion engine.
It is a further object of this invention to provide an improved cylinder head assembly for a multi valve engine wherein there are a plurality of valves actuated by thimble tappets and yet a single cylinder head assembly may be employed without resorting to two piece construction.
It is a further object of this invention to provide a tappet arrangement for the cylinder head of an internal combustion engine that permits a one piece cylinder head assembly and adequate and accessible fasteners for affixing the cylinder head to an associated cylinder block.